1. Field of the Invention
The invention relates to a lid closure and lift mechanism and, more particularly, to a counter balance spring assembly.
2. Description of the Background Art
In a wafer processing system, a lid assembly for a processing chamber is typically rather heavy. To ensure safety for operating personnel, various mechanisms have been used to facilitate the closing or opening of the lid--for example, by reducing the force necessary to effect movement of the lid. In one arrangement, gas springs, or cylinders, are mounted onto a lid assembly to provide a force to assist lifting the lid during opening. Another arrangement uses a spring mechanism which generates a restoring force in response to an external torsional force exerted on the spring during closing or opening of the lid. Typically, a spring is housed inside a hinge-like structure, and is subjected to a torsional force when the lid is opened or closed. This torsional force leads to a compression of the spring, which in turn generates a restoring force resulting in an opposite torsional component. However, the torsional motion in such a mechanism causes particulate contamination due to friction between the spring and its housing. For wafer processing applications, such particulate contamination has to be minimized to avoid decreasing yields on the wafers.
Therefore, there is an ongoing need for alternative counter balance mechanisms which facilitate the opening and closing of lids, while minimizing particulate contamination for wafer processing systems.